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Technique to Determine Life and Effectiveness of Glycerian/ EDTA

IP.com Disclosure Number: IPCOM000052876D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Senger, RC: AUTHOR

Abstract

There has not been a satisfactory way to determine the life or the effectiveness of the flux in the immersion solder process in performing its intended function. Techniques that are being used monitor the physical make-up of the solution, such as PH, percent EDTA, percent impurities, and viscosity. There has not been a strong correlation found between any of these parameters and the goodness of the flux.

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Technique to Determine Life and Effectiveness of Glycerian/ EDTA

There has not been a satisfactory way to determine the life or the effectiveness of the flux in the immersion solder process in performing its intended function. Techniques that are being used monitor the physical make-up of the solution, such as PH, percent EDTA, percent impurities, and viscosity. There has not been a strong correlation found between any of these parameters and the goodness of the flux.

Recent studies indicate that a galvanic potential difference exists between printed circuit boards to be soldered and the grounded machine body (titanium, stainless steel, SnBi solder, etc.) containing the glycerin/EDTA flux. On immersion-tinned parts, this potential difference is initially positive when the part is submerged into the heated flux and slowly progresses to a negative potential with time in the solution. The time that is required is also dependent on the temperature of the solution.

It has been determined that the cause of this polarity reversal is the presence of tin oxides and the subsequent removal of these oxides while the parts are submersed in the flux. Determination of the life of the flux is then a matter of measuring the galvanic potential difference of standard immersion-tinned samples (oxinade coated) submersed in the flux with respect to a reference electrode, such as, titanium. Optimum fluxing action can also be determined as a function of temperature, percent chelate, and...